Modern disc drives are commonly used in a multitude of computer environments, ranging from super computers to notebook computers, to store large amounts of data in a form that is readily available to a user. Typically, a disc drive has one or more magnetic discs that are rotated by a spindle motor at a constant high speed. Each disc has a data storage surface divided into a series of generally concentric data tracks that are radially spaced across a band having an inner diameter and an outer diameter. The data is stored within the data tracks on the disc surfaces in the form of magnetic flux transitions. The flux transitions are induced by an array of read/write heads. Typically, each data track is divided into a number of data sectors where data is stored in fixed size data blocks.
The read/write head includes an interactive element such as a magnetic transducer. The interactive element senses the magnetic transitions on a selected data track to read the data stored on the track. Alternatively, the interactive element transmits an electrical signal that induces magnetic transitions on the selected data track to write data to the track.
Each of the read/write heads is mounted to a rotary actuator arm and is selectively positioned by the actuator arm over a pre-selected data track of the disc to either read data from or write data to the data track. The read/write head includes a slider assembly having an air bearing surface that, in response to air currents caused by rotation of the disc, causes the head to fly adjacent to the disc surface with a desired gap separating the read/write head and the corresponding disc.
Typically, multiple center-open discs and spacer rings are alternately stacked on a spindle motor hub. The hub, defining the core of the stack, serves to align the discs and spacer rings around a common axis. Collectively the discs, spacer rings and spindle motor hub define a disc stack envelope. The surfaces of the stacked discs, forming a disc stack, are accessed by the read/write heads which are mounted on a complementary stack of actuator arms which comprise an actuator assembly, or E-block. The E-block generally includes head wires which conduct electrical signals from the read/write heads to a flex circuit which, in turn, conducts the electrical signals to a flex circuit connector mounted to a disc drive basedeck. A general discussion of E-block assembly construction can be found in U.S. Pat. No. 5,404,636 entitled METHOD OF ASSEMBLING A DISC DRIVE ACTUATOR, issued Apr. 11, 1995, to Stefansky et al., and assigned to the assignee of the present invention.
When the disc drive is not in use, the read/write heads are parked in a position separate from the data storage surfaces of the discs. Typically, a landing zone is provided on each of the disc surfaces where the read/write heads are positioned before the rotational velocity of the spinning discs decreases below a threshold velocity which sustains the air bearing. The landing zones are generally located near the inner diameter of the discs.
Once the heads are positioned in the landing zones, it is necessary to secure the actuator assembly by a latching arrangement to prevent the heads from subsequently moving out onto the data surfaces of the discs while the disc drive is not in use. Latching arrangements are well known in the art and have included various configurations of springs, solenoids and magnets to secure and release the actuator. For example, see U.S. Pat. No. 5,187,627 entitled MAGNETIC LATCH AND CRASH STOP, issued Feb. 16, 1993, to Hickox and Stram; U.S. Pat. No. 5,224,000 entitled CRASH STOP AND MAGNETIC LATCH FOR A VOICE COIL ACTUATOR, issued Jun. 29, 1993, to Casey and West; and U.S. Pat. No. 5,231,556 entitled SELFHOLDING LATCH ASSEMBLY, issued Jul. 27, 1993, to Blanks. All of these references are assigned to the assignee of the present invention.
In addition to the latch mechanisms mentioned above, there have been efforts to couple the operation of a latching device with the airflow generated by the rotation of the discs. That is, it is known to use the energy of the air currents generated by the rotation of a plurality of stacked discs to release a passive, spring-loaded aerodynamically responsive latch. For example, such latches are taught in U.S. Pat. No. 4,647,997 entitled AERODYNAMIC LATCH FOR DISK FILE ACTUATOR, issued Mar. 3, 1987, to Westwood; and U.S. Pat. No. 5,043,834 entitled ACTUATOR LOCKING SYSTEM OF DISK UNIT, issued Aug. 27, 1991, to Kubo, Masuda and Nakagawa.
Associated problems with such devices have limited the application in which they can be used. For example, a continuing trend in the industry is the reduction in size of modern disc drives. As a result, the discs of modern disc drives increasingly have smaller diameters and tighter spacings. Although providing increasing amounts of storage capacity, narrow vertical spacing of the discs gives rise to a problem of increased sensitivity to external mechanical shock. Additionally, as disc drives continue to decrease in size, smaller heads, thinner substrates, longer and thinner actuator arms and thinner gimbal assemblies continue to be incorporated into the disc drives. These factors significantly increase the need to protect the disc drives from incidental contact between the actuator arm/gimbal assemblies and the disc surfaces. Furthermore, market requirements demand ever increasing non-operating shock performance.
Consequently, there has not been available a latching device which will universally meet the ever increasing demands of disc latching that will protect the discs from the deleterious effects of non-operational shock such as can occur during shipping and handling. Protection from this and other non-operating mechanical shocks continue to be a major problem to the industry.
Another problem with prior art aerodynamic actuator latches is that they have a tendency to release the actuator prematurely. The prior art teaching commonly includes a spring-biased lever which abuts the actuator on one end to secure it in place when the disc drive is not operating. The other end of the lever typically has a vane which is deflected by the air current generated by the spinning discs when the disc drive is operating. The air current shifts the lever to a non-biased position where the first end clearingly disengages the actuator so that the actuator can freely move. A common problem, however, is associated with the fact that only a relatively small torque is necessary to release the lever, typically less than 2 gram-meters. Movement of the lever is easily triggered by non-operating torques because forces greater than this magnitude and more are very common in normal shipping and handling activities. Such non-operating forces often result in the disengagement of the lever from the actuator while the disc drive is not operating. Since the discs are not spinning there is no air bearing, so a free moving actuator can cause the read/write heads to contact the data storage tracks, likely causing damage to the data storage surfaces.
Accordingly, there is a need for an improved aerodynamically driven latch apparatus for a disc drive to reduce the susceptibility of damage to the disc drive as a result of non-operating mechanical shocks.